1. People’s Place in Nature
Chapter 6

2. Taxonomy
The science of classifying organisms into different categories
Each plant or animal is known by a binomen, or two-part name consisting of a generic and a specific name. This is the system of binomial nomenclature.
For example, the binomen for humans is Homo sapiens.
Taxa above the level of genus are referred to as “higher taxa”
There are five major higher taxa: kingdom, phylum, class, order and family.
This can be expanded by the use of prefixes and other terms, such as: suborder and superfamily

3. Principles of Classification
A comparison between two animals may reveal many anatomical correspondences
Homologies
Similarities based on, and shared by, a common ancestor
Analogies
Similarities based on common function, with no assumed common evolutionary descent
Homoplasy
Separate evolutionary development of similar characteristics in different groups of organisms
A characteristic shared by a set of species but not present in their common ancestor
Ex: Independent eye development

4. Evolutionary Relationships
Homoplasy can develop in four different ways:
Parallelism – development of similar characteristics separately in two or more lineages of common ancestry
Convergence - development of similar characteristics separately without common ancestry
Analogy – Development of similar function with no common ancestry
Chance – Similarity in characteristics developed completely independently

5. Homologies
Similarities in the forelimb bones of these animals can be most easily explained by descent from a common ancestor

6. Cladistics
Cladistics - Attempts to make rigorous evolutionary interpretations based solely on analysis of certain types of homologous characters
Clade - Lineage, or a group of organisms sharing a common ancestor
The group includes the common ancestor and all descendants
Clades are nested, one in another, as each branch in turn splits into smaller branches

7. Ancestral and Derived Characteristics
Can only be used when comparing two species
Ancestral (Primitive)
Characters inherited by a group of organisms from a remote ancestor and not diagnostic of groups that diverged after the character appeared
A trait that was retained by a species from its ancestor and is shared by two organisms
Derived (Modified)
Characters that are modified from the ancestral condition and thus are diagnostic of particular evolutionary lineages
Trait that has evolved after break off from common ancestor

8. An Example of Cladistic Analysis: Evolution of Cars and Trucks
From a common ancestor of all passenger vehicles, the first major divergence is between cars and trucks (I)
A later divergence occurs between luxury cars and sports cars (II)
Derived features of each grouping appear after its divergence from other groups

9. An Example of Cladistic Analysis: Evolution of Cars and Trucks (cont’d)
In this “tree,” SUVs diverge from trucks, but like sports cars, have a decorative racing stripe
This is a homoplasy and does not make SUVs sports cars
Classifications based on one characteristic that can appear in different groups can lead to an incorrect conclusion

10. The Chordates Animalia – Kingdom that includes 20 major phyla
Chordata – the phyla which includes all animals with a nerve cord, pharyngeal slits, and supporting cord along the back
Humans belong to the phylum Chordata
Vertebrates - Animals with segmented, bony spinal columns
Sub-phylum of Chordata
In place of a notochord, a true vertebral column, or spine, has developed
Includes fish, amphibians, reptiles, birds, and mammals
The origin of land vertebrates also depended on the evolution of limbs

11. The Mammals
Homoeothermic - can control their body temperature through physiological means
Hair or fur provides a layer of insulation
Heterodont dentition - teeth consist of different sizes and functions
Incisors, canines, premolars, molars
Most offspring develop inside the mother
Monotremes (prototherians) – primitive mammals that lay eggs
Therians – marsupial and placental mammals
Mother’s mammary glands for infant feeding

12. Teeth Reptilian teeth (top) are homodont
Mammals are heterodont, they have different kinds of teeth; incisors, canines, premolars, and molars

13. The Mammalian Brain
Mammals are characterized by improvements in the nervous system and elaboration of the brain
Most mammalian behavior is learned
Can record memories that produced positive and negative reactions to experiences
Leads to feelings and emotion
Limbic System – Section of the mammalian brain with three main structures
Hippocampus - primarily associated with memory and spatial navigation
Amygdala - enter for emotions, emotional behavior, and motivation
Hypothalamus – Responsible for production of hormones that control temperature regulation, thirst, hunger, sleep, mood, and sex drive